a3a046dc62
* Updates maven to 3.9.0 * Migrate Structure * Insert explicit ids for headers * Remove unnecessary asciidoc attributes * Copy default antora files * Fix indentation for all pages * Split files * Generate a default navigation * Remove includes * Fix cross references * Enable Section Summary TOC for small pages * More antora customization
103 lines
3.4 KiB
Plaintext
103 lines
3.4 KiB
Plaintext
[[spring-cloud-zookeeper-discovery]]
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= Service Discovery with Zookeeper
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Service Discovery is one of the key tenets of a microservice based architecture. Trying to
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hand-configure each client or some form of convention can be difficult to do and can be
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brittle. https://curator.apache.org[Curator](A Java library for Zookeeper) provides Service
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Discovery through a https://curator.apache.org/curator-x-discovery/[Service Discovery
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Extension]. Spring Cloud Zookeeper uses this extension for service registration and
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discovery.
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[[activating]]
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== Activating
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Including a dependency on
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`org.springframework.cloud:spring-cloud-starter-zookeeper-discovery` enables
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autoconfiguration that sets up Spring Cloud Zookeeper Discovery.
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NOTE: For web functionality, you still need to include
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`org.springframework.boot:spring-boot-starter-web`.
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CAUTION: When working with version 3.4 of Zookeeper you need to change
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the way you include the dependency as described xref:install.adoc[here].
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[[registering-with-zookeeper]]
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== Registering with Zookeeper
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When a client registers with Zookeeper, it provides metadata (such as host and port, ID,
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and name) about itself.
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The following example shows a Zookeeper client:
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[source,java,indent=0]
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----
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@SpringBootApplication
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@RestController
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public class Application {
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@RequestMapping("/")
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public String home() {
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return "Hello world";
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}
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public static void main(String[] args) {
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new SpringApplicationBuilder(Application.class).web(true).run(args);
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}
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}
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----
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NOTE: The preceding example is a normal Spring Boot application.
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If Zookeeper is located somewhere other than `localhost:2181`, the configuration must
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provide the location of the server, as shown in the following example:
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[source,yml,indent=0]
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.application.yml
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----
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spring:
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cloud:
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zookeeper:
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connect-string: localhost:2181
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----
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CAUTION: If you use xref:config.adoc[Spring Cloud Zookeeper Config], the
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values shown in the preceding example need to be in `bootstrap.yml` instead of
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`application.yml`.
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The default service name, instance ID, and port (taken from the `Environment`) are
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`${spring.application.name}`, the Spring Context ID, and `${server.port}`, respectively.
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Having `spring-cloud-starter-zookeeper-discovery` on the classpath makes the app into both
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a Zookeeper "`service`" (that is, it registers itself) and a "`client`" (that is, it can
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query Zookeeper to locate other services).
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If you would like to disable the Zookeeper Discovery Client, you can set
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`spring.cloud.zookeeper.discovery.enabled` to `false`.
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[[using-the-discoveryclient]]
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== Using the DiscoveryClient
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Spring Cloud has support for
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https://docs.spring.io/spring-cloud-openfeign/docs/current/reference/html/[OpenFeign]
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(a REST client builder), `RestTemplate` and `WebClient` via https://docs.spring.io/spring-cloud-commons/reference/spring-cloud-commons/loadbalancer.html#spring-cloud-loadbalancer-integrations[Spring Cloud Loadbalancer], using logical service names instead of physical URLs.
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You can also use the `org.springframework.cloud.client.discovery.DiscoveryClient`, which
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provides a simple API for discovery clients that is not specific to Netflix, as shown in
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the following example:
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[source,java,indent=0]
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----
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@Autowired
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private DiscoveryClient discoveryClient;
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public String serviceUrl() {
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List<ServiceInstance> list = discoveryClient.getInstances("STORES");
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if (list != null && list.size() > 0 ) {
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return list.get(0).getUri().toString();
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}
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return null;
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}
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----
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